Ubon Ratchathani is one of the four major cities of Isan, also known as the "big four of Isan." The city is on the Mun River in the southeast of the Isan region of Thailand, and is located 615 km (382 mi) away from Bangkok. It is known as Ubon (อุบลฯ) for short. The name means "royal lotus city". Ubon is the administrative center of Ubon Ratchathani Province.

Northeast Thailand or Isan consists of 20 provinces in northeastern Thailand. Isan is Thailand's largest region, on the Khorat Plateau, bordered by the Mekong River to the north and east, by Cambodia to the southeast and the Sankamphaeng Range south of Nakhon Ratchasima. To the west it is separated from northern and central Thailand by the Phetchabun Mountains. Isan covers 167,718 km2 (64,756 sq mi), making it about half the size of Germany and roughly the size of England and Wales. The total forest area is 25,203 km2 (9,731 sq mi) or 15 percent of Isan's area.